<!DOCTYPE HTML>
<html>
<head>
<meta charset="utf-8" />
<meta name="renderer" content="webkit" />
<title>kid</title>
</head>
<body>
<button id="close">close all kids</button>
</body>
<script>
document.querySelector('#close').addEventListener('click', e => {
	window.opener.postMessage('close', 'https://sandii.github.io/post-msg/parent.html');
}, false);
</script>
</html>